Title

Author

Degree Type

Thesis

Date of Award

2015

Degree Name

Master of Science

Department

Horticulture

First Advisor

William R. Graves

Abstract

Nyssa biflora Walt. (swamp tupelo) and Nyssa sylvatica Marsh. (black gum) are closely related species of trees native to North America. Although N. sylvatica is prevalent in the nursery trade, little is known about the horticultural potential of N. biflora. Because many authors referred to N. biflora as a variant of N. sylvatica, taxonomic confusion may have resulted in the overlooking of N. biflora for use as a horticultural plant. The overarching objectives of my research were to establish seed-propagation protocols for N. biflora and to characterize the responses of seedlings of N. biflora to water stress. We included N. sylvatica in all experiments to provide a basis for comparison with N. biflora. The germination experiment was designed to test for effects of time of stratification on cleaned seeds (depulped seeds with endocarp intact) of N. biflora and N. sylvatica; seeds within intact fruits of N. biflora were also included. We found the pulp of fruit of N. biflora to have inhibitory effects on germination of seeds. Stratification had a more pronounced effect on N. sylvatica than N. biflora, and we conclude N. biflora is less resistant to germination. The water-stress experiment was designed to test for effects of a wide range of root-zone moisture contents on photosynthesis, water potential, and biomass accumulation of both species of Nyssa. Rates of photosynthesis of N. biflora receiving treatments of drought cycles were greater than those of N. sylvatica after two weeks, thus, N. biflora may be better adapted to short periods of drought than N. sylvatica. Rate of dry mass accumulation and increase in height of N. biflora were greater than those of N. sylvatica across all treatments of flooding and drought. N. biflora displayed a tolerance to flooded root zones that was superior to that of N. sylvatica. Adventitious roots and hypertrophied lenticels were formed on flooded plants of N. biflora. We conclude that N. biflora can be propagated easily from seed, is more resistant to water stress than is N. sylvatica, and deserves further investigation for its potential in horticulture.